I. Field of the Invention
The invention relates to frequency tracking methods and apparatus, in particular, multiple loop based frequency tracking methods and apparatus.
II. Description of the Related Art
Frequency tracking apparatus and methods commonly must balance a large pull-in range against small, steady-state frequency errors. To limit/reduce steady state errors, some apparatus and methods sequentially employ a large pull-in range tracking loop and then an accurate fast-tracking frequency loop. These apparatus and methods in practice have limitations including convergence and sequential switching control. Thus, a need exists for frequency tracking apparatus and methods that may efficiently pull in large frequency errors while having a small steady state frequency error.